A system used between two or more men to help aid them in the event they are caught in an uncomfortable member of the opposite sex, particularly an unattractive and/or obese female during a party situation. When utilizing this system, the male victim will shout out "BUDDY!" and in turn the nearest member(s) of the buddy chain will come to his rescue.
Nasty party slut: Wanna get out of here?
Victim: Uh, well see...(looking around) uh, BUDDY!
Friend/Wingman (shuffles over to the rescue): So, uh John, you left your laundry downstairs. Oh, then we're up for beer pong. LETS GO.
Victim: Wow thanks man...the buddy system never fails. Did you see her snaggletooth?
A system used against your friends whenever you need them to do something they refuse to do. Often used as a last resort of begging.
Usually applies to the "You help me, I help you" or the "Because we're buddies, you should totally do this for me" sayings.
Jen: "No tom, I will not have sex with you!"
Tom: "But Jen! What about the buddy system?!"
Jen: "...Alright, fine -_-"